1. The Field of the Invention
The present invention relates generally to the field of rendering graphics. More particularly, embodiments of the invention relate to rendering changed portions of composited images.
2. The Relevant Technology
Advances in technology have led to a surge in electronic devices. Personal audio players (e.g., mp3 players), personal digital assistances, personal video players, satellite radios, and the like are examples of devices that people use everyday. Many of these devices are wireless. As with most devices, the cost of these devices can vary widely and can depend on the various features that may be included with a particular device.
One of the features that most of these devices have in common, however, is a display. The display is often an integral part of the device and can have a substantial impact on user satisfaction. The ability of a device to provide a rich visual experience can often depend on the graphic capabilities of the device. However, the ability to process graphics comes at a cost.
When a graphic system is composited, for example, it is often the case that multiple layers are drawn or painted to the display. The preparation of a given frame often includes multiple steps. For instance, the background is typically created first. Then, images are placed over the background. Finally, text may be included as yet another layer. In each instance, each of these layers is fully drawn independently of the other layers. When animation or transparency is also introduced, and the display must be redrawn multiple times each second, the computational complexity of the graphics operation increases because it becomes necessary to redraw or repaint the display.
There is therefore a tension that exists between the capabilities of a device, including graphical capabilities, and the cost of the device. This is balanced with the desire of a provider to provide a rich graphical experience to the user. Systems and methods are therefore needed that enable a device to present a rich graphical experience at reduced cost.